This invention relates to digital communication such as satellite broadcasting and, more particularly, to increasing the information acquiring process speed for long term programs.
FIG. 22 schematically illustrates a state of sending satellite broadcasting radio waves as a simplified conceptual chart. Radio waves from a ground station 2 are set through a broadcasting satellite 4 to the ground. From the broadcasting satellite 4 are sent out a plural number of transport streams (transmission routes determined by frequency, plane of polarization, etc.) TS1, TS2, and TS3. Furthermore a plural number of services SV11, SV12, SV13, and SV14 (corresponding to channels in the ground wave broadcasting) are multiplexed by time division in packets in the transport stream TS1. Similarly, services SV21, SV22, SV23, and SV24 are multiplexed in the transport stream TS2, and services SV31, SV32, SV33, and SV34 are multiplexed in the transport stream TS3. To the transport streams are also sent out program information and control data associated with the packeting or the like in addition to video data and audio data for respective services. While FIG. 22 shows only three transport streams, much more transport streams are actually sent out. Furthermore, while FIG. 22 shows four services multiplexed for each transport stream, in actuality much more services are multiplexed.
FIG. 23 shows video data, audio data, control data, and program information multiplexed in the transport streams TS1, TS2, and TS3. In the transport stream TS1 are multiplexed: audio data ES(A)11 and video data ES(V)11 of the service SV11; audio data ES(A)12 and video data ES(V)12 of the service SV12; . . . , and audio data ES(A)14 and video data ES(V)141 of the service SV14. For each of the services SV11, SV12, SV13, and SV14 are also multiplexed currently broadcast program information P_EIT11, P_EIT12, P EIT13, and P_EIT14, and information F_EIT11, F_EIT12, F_EIT13, and F_EIT14 of programs to be broadcast next. Furthermore, an SDT1 describing the details of the service multiplexed in the transport stream TS1, an SDT2 describing the details of the service multiplexed in the transport stream TS2, and an SDT3 describing the details of the service multiplexed in the transport stream TS3 are also multiplexed and transmitted.
Incidentally, audio data, video data, and program data are multiplexed also in other transport streams TS2 and TS3. However, for the long-term program information S_EIT11, S_EIT12, . . . , S_EIT14, S_EIT21, S_EIT22, . . . , S_EIT24, S_EIT31, S_EIT32, . . . , S_EIT34, and S_EIT41, S_EIT42, . . . , S_EIT44, the information is multiplexed only in the transport stream TS2 because the amount of information is large.
In some services, the long term program information is not provided for reasons such as that always the same contents are broadcast. Therefore, in the control data SDT1, SDT2, and SDT3 of the transport stream TS2, there is described the information on whether the long term program information S_EIT is present or not for the services SV11 to SV14, SV21 to SV24, and SV31 to SV34. However, the presence information is described only for the control data SDT1, SDT2, and SDT3 of the transport stream TS2 in which the long-term program information S_EIT is multiplexed. In the control data SDT1, SDT2, and SDT3 of other transport streams TS1 and TS3, areas for describing the presence information is provided, but their contents are all described as xe2x80x9cnilxe2x80x9d and no substantial presence information is described.
Each piece of the above-described information is transmitted in packets as shown with 60a in FIG. 24. That is to say, video data and audio data of each service are multiplexed in packets and transmitted. After the transmission with 60a, transmission with 60b follows. Incidentally, a packet ID is attached to ES in packet of each service, The packet ID of ES of each service is arranged to be recognized with control data PAT and PMT, With such an arrangement, the ES for each service may be acquired selectively. While FIG. 24 is shown for the transport stream TS1, the same applies to other transport streams TS2 and TS3.
Furthermore, control data NIT is multiplexed in each of the transport streams TS1, TS2, and TS3. In the control data NIT are described transmission specifications (frequencies, etc.) of the transport streams TS1, TS2, and TS3, and service names (service IDs) included in those transport streams. This makes is possible to learn what kinds of services are included in each of the transport streams. In the control data NIT is also described the information showing in which transport stream the long term program information is written.
FIG. 25 roughly shows a satellite broadcasting receiver. A transport stream is selected with a tuner 8, and a described service is separated with a decoder 10. From the decoder 10 are output selected audio data and video data. A microprocessor (MPU) 12 sets a packet ID of the ES of a desired service to the decoder 10. This causes the decoder 10 to output the ES of the service. When the packet ID of the control data is set to the decoder 10, separated control data is given to the MPU 12.
Assuming that the service SV33 of the transport stream TS3 is currently being received, operation of a case will be described below in which a command is given to the MPU 12 to switch to the service SV12 of the transport stream TS1. First, the MPU 12 takes in control data NIT (See FIG. 23) by controlling the decoder 10 (namely by setting the packet ID of the control data NIT). It is learned from the description of the control data that the service SV12 to be received is multiplexed in the transport stream TS1. Next, the transport stream TS1 is received by controlling the tuner 8. Further, the decoder 10 is controlled to acquire the control data PAT1 and PMT12, and to acquire packet IDs of the video data ES(A) 12 and audio data ES(V)12. Next, this packet ID is set to the decoder 10 so that the video data (ES(A) 12 and audio data ES(V)12 of the intended service SV12 are output from the decoder 10. Switching to the service to be received is carried out as described above.
Incidentally, a future broadcasting schedule of any of the services may be learned by acquiring the long term program information of S_EIT of the service in question. The long term program information S_EIT includes genre information on each event (so-called program) broadcast in each service. Therefore, once the long term program information S_EIT is acquired, it is possible to search and display broadcasting schedules in specific genres.
Assuming that the service SV12 is currently being received, the process of acquiring the long term program information S_EIT will be described below. First, the MPU 12 controls the decoder 10 to separate and acquire the control data NIT. From the description of the control data NIT, a transport stream is known where the long term program information S_EIT is multiplexed, and the tuner 8 is controlled to receive the transport stream TS2. Further, the decoder 10 is controlled to separate and acquire the control data SDT1, SDT2, and SDT3, and to acquire the presence information for the long term broadcasting program in each service.
According to the presence information, the MPU 12 controls the decoder 10 for only the service in which the long term program information is present, and acquires the long term program information.
As described above, the long term program information may be acquired for each service. The acquired long term program information may be displayed as it is, or searched according to the genre information to display program information only in a specific genre.
However, with the conventional art described above, the following processes are required to acquire the long term program information: (1) to switch to receive the transport stream in which the presence information for the long term program information is multiplexed, (2) to acquire the presence information in the switched transport stream, and (3) to acquire the long term program information in the required service according to the presence information. Therefore, there is a problem that a long time is taken before the long term program information appears on the display screen when the receiver is operated by a receiving person intending to display the information.
The object of the invention is to provide a digital communication capable of solving the above-described problem and quickly acquiring the long term program information.
Means for Solving the Problem and the Effect of the Invention
This invention is characterized in that,
on a sending side,
at least one transport stream is assumed as a specified transport stream, long term program information for each service is multiplexed in the specified transport stream, and, for each service, presence information on whether the long term program information is multiplexed in the specified transport stream is multiplexed in all the transport streams including at least one service, and
on a receiving side,
the presence information for each service multiplexed in the transport stream currently being received is acquired and retained beforehand, and if it is necessary to learn the presence or absence of the long term program information for the service, whether the long term program information for the service is present is determined from the retained presence information.
Since the presence information for the long term program information is multiplexed also in the transport streams other than the specified transport stream, the presence information may be acquired even when a transport stream other than the specified transport stream is being received. In particular, if the multiplexing is made in all the transport streams, the presence information may be acquired and retained beforehand irrespective of whichever transport stream being current received. Therefore, in the case the long term program information is required, the information may be quickly acquired by switching the transport stream and then immediately acquiring the information according to the retained presence information.
Furthermore, by multiplexing the presence information also in all the transport streams that do not include service, the presence information may be acquired even when such transport streams are being received.
In this invention, the presence information is described on a service description table (SDT). In any transport stream, the service description table has an area for describing all the services of all the transport streams (description loops for respective transport streams). Therefore, the presence information for each service may be easily described.
In this invention, the presence information is described on a network information table (NIT). In any transport stream, the network information table has an area for describing all the services of all the transport streams. Therefore, the presence information for each service may be easily described.
In this invention, the receiver is adapted to acquire and retain the presence information for all the services at specified time intervals during the receiving operation. Therefore, the presence information is renewed to the latest at the specified time intervals.
In this invention, the receiver is adapted to acquire and retain the presence information for all the services when the power supply is off. Since the receiving person does not make the receiving operation while the power supply is off, acquisition of the presence information can take time.
In this invention, the acquired long term program information is searched on the receiving side. Therefore, the long term program information in restricted genres may be quickly displayed.
In this invention, xe2x80x9clong term program information multiplexing meansxe2x80x9d refers to the means for multiplexing long term program information in the transport streams. In the embodiment, it refers to the generating part SG2 and the multiplexing part MX2 in FIG. 1.
The xe2x80x9clong term program informationxe2x80x9d refers to the information including at least the information on the program to be broadcast after the program to be broadcast next to the current program. In the embodiment, the program in question refers to S_EIT in FIG. 20. Here, the xe2x80x9cprogramxe2x80x9d refers to the index information of the contents sent by broadcasting. The concept of program referred to here also includes predetermined broadcasting plan for broadcasting computer programs and data.
The xe2x80x9cpresence informationxe2x80x9d multiplexing means refers to the means for multiplexing the presence information in the transport stream. In the embodiment, it refers to the SI generating part SG1, and the SC3 multiplexing parts MX1 and MX3 in FIG. 1.
The xe2x80x9cpresence informationxe2x80x9d is the information that indicates whether the long term program information for the service is multiplexed in the specified transport stream. In the embodiment, it refers to the descriptors () in FIGS. 14, 15 and 16. It also refers to the EIT schedule Flag in FIG. 15.
The xe2x80x9cspecified transport streamxe2x80x9d refers to the transport stream in which the long term program information is multiplexed. In the embodiment, it refers to the transport stream TS2. While there is only one specified transport stream in the embodiment, there may be a plural number of specified transport streams.
The xe2x80x9cpresence information retaining meansxe2x80x9d refers to the means for acquiring and retaining the presence information. In the embodiment, it refers to the CPU 847 in FIG. 8 (especially steps S34, S35, and S36) and the service information management memory 842.
The xe2x80x9clong term program information acquisition meansxe2x80x9d refers to the means that determines the presence or absence of the long term program information, and acquires the long term program information for only the services where the long term program information is present. In the embodiment, it refers to the CPU 847 in FIG. 8(in particular the steps S47 and S48).
The xe2x80x9creceiverxe2x80x9d refers to the device that is capable of selectively receiving required transport stream and service from a plural number of transport streams. This concept includes the receivers or the like including the so-called set-top box and the CRT.
The xe2x80x9crecording medium with recorded programsxe2x80x9d refers to the recording medium such as the ROM, RAM, hard disk, flexible disk, CD-ROM or the like on which programs that can be executed with a CPU are recorded. Here, the program also includes not only those which can be executed directly with a CPU but also those which must be once installed, is compressed or coded.